The invention relates to a method of manufacturing a stack of embossed foil webs for a vehicle heat shield, a stack manufactured by this process, and a device for the manufacture of a stack of this kind.
Foil stacks of this kind are used, for example, as heat or as sound insulation, and consist of several profiled foil sheets lying on top of one another, for instance made of non ferrous metals, in particular of aluminium. The stacks described in the following are used preferably in the motor vehicle industry, in particular as sound absorbing insulation packs or as heat shields for vehicles.
For the manufacture of stacks of this kind, flat or sheet material is passed through a pair of embossing rollers, of which in general one of the rollers has the desired structure, whilst the other either has an elastic surface or is provided with a complementary structure (negative structure). The structuring/embossing of the flat material is combined with local stretching or elongation of the flat material. Examples of structuring of flat or sheet materials done in such a way are sufficiently well known to the specialist. This structuring or embossing can be in the form of knobs, corrugations or diamond shapes.
Sound absorbing insulation packs or heat shields, which are used, in particular, in vehicle or motor vehicle construction, generally consist of several structured flat or sheet materials arranged on top of one another, especially in the form of embossed foils or metal sheets. The structured flat materials for creating an insulating effect are designed in such a way that air or gas volumes can form between the individual layers and contact between the layers arranged on top of one another is avoided over a large area. The individual sheets should therefore be as far apart from one another as possible. In order to achieve considerable embossing depths, the distances between the individual deformations are increased, which, however, leads to a reduction in bending strength and compression resistance. This kind of deformation of flat materials leads, therefore, to the disadvantage that the structured flat material is easily pressed back together again even at low surface pressure, which can occur, for example, by unintentional or undesirable pressing actions, and hence the insulation effect is lost. The low compression resistance of these structure flat materials is due both to the low number of deformations per surface unit (in the following also referred to as structural density, or knob or corrugation density) and also to the low thickness of the structured flat materials caused by the extension or stretching during embossing. As a consequence of the reduced structural density and the locally reduced material thickness, these flat materials have an inadequate rigidity for their intended purpose in the area of individual deformations (knobs, corrugation crests and depressions). This leads to the fact that with known knobbed flat materials, for example, the individual knobs can be pressed flat again or deformed even under slight pressure. Furthermore, these structured flat materials have a low overall bending strength, as they have a low compression resistance and low rigidity in the area of the individual knobs.
DE - 43 ""29 ""411 describes a heat and sound insulation material made of several profiled foils, the said foils having a corrugated profile formed from parallel corrugation crests and depressions, with gussets folded into the depressions. However, practice has shown that these foil packs only meet the expectations of the motor vehicle industry in part. In addition, it has proved that the rigidity in the area of the individual corrugation crests and depressions is not adequate for the use referred to above.
With the process for manufacturing foil stacks known today, a foil web is passed through a pair of rollers and the foil web, thus embossed, is cut into sections, which are laid or stacked on top of one another. Processes are also known where several pairs of rollers are used at the same time, and the embossed foil webs are passed over one another and cut together. With all these processes it may happen that the embossed foils become interlocked in one another, i. e., the individual embossings come to lie exactly over one another and the individual foils therefore slot into one another (in a similar way to a stack of egg boxes). This means that the individual foils are not at a distance from one another in the intended way, but lie instead closely on top of one another.
From the printed publication EP 0 439 046 A1, a process and a device for the manufacture of a foil stack is known, where several embossing rollers are used. This manufacturing process also proves to be exceedingly complex and is correspondingly cost intensive. In order to be able to change the structure of the foils or the flat or sheet material, with this device a large number of embossing rollers must be exchanged.
In the following the concept of xe2x80x9cfoil webxe2x80x9d will be used to include all types of sheet metal, flat or sheet material. The concept xe2x80x9csheetsxe2x80x9d is to be used to all types of stacked sheet metal, flat or sheet material which is cut from the processed foil webs. It is a matter of course that this material in the form of a web may consist of processed paper, suitable plastics or metal, unperforated or perforated foils, thin metal leaf or metal sheets, for example. These materials can also be layered and/or have slight deformation patterns, perforations or fissures.
An essential task of this invention is to create a cost effective process and a device for the manufacture of an insulation pack for vehicle heat shields, which has a good heat insulation effect and good sound absorption. Furthermore, this insulation pack is to have a high bending strength and high compression resistance.
A further task of this invention is to create an embossed foil web which does not have the disadvantages of the known foil webs. In particular, it is the task of this invention to create a foil web which has increased rigidity and, in particular, increased bending strength and higher compression resistance.
It is also a task of this invention to create a stack made of embossed foil webs, the said stack being suitable for use as a sound absorbing vehicle heat shield, and where the individual sheets of the said stack are certain to remain lying at a distance from one another. In particular, the task is to create a stack which has increased bending strength and higher compression resistance.
The task is solved by a method of manufacturing a stack made of embossed foil webs for a vehicle heat shield, where at least two unembossed foil webs are conveyed from a feed device in a conveying direction and are embossed, in particular knobbed, between at least one pair of embossing rollers, and the embossed foil webs are then brought together to form a stack in a stacking device wherein the embossed foil webs arranged next to one another are conveyed along different conveying routes with the aid of a conveying device in such a way that at least two embossed foil webs arranged next to one another in the stack are in the conveying direction due to the differences in length of the various conveying routes.
Preferably (including advantageously) the unembossed foil webs lying over one another are embossed by a single pair of embossing rollers. Preferably the embossed foil webs lying on top of one another are embossed with at least two different embossing patterns, including a first embossing pattern and a second embossing pattern. Preferably the first and second embossing patterns in the conveying direction are essentially structured to be of the same length, and that the embossed foil webs are guided along different length conveying routes in such a way that two foil webs arranged next to one another in the stack have a different embossed pattern.
It is preferred that the unembossed foil webs lying on top of one another are overstretched in a predetermined way during embossing, so that the embossed foil webs are provided with deformations, in particular knobs, with a draped or folded type structure, and fissures are preferably created.
A device according to the invention for manufacturing a stack made of embossed foil webs for a vehicle heat shield, includes a feed device for several unembossed foil webs, at least one pair of embossing rollers arranged to follow the feed device in a conveying direction for embossing the unembossed foil webs, which are arranged to lie over one another, and a stacking device arranged to follow this, for bringing together the embossed foil webs, whereas a conveying device is arranged between the at least one pair of embossing rollers and the stacking device, for creating different route lengths for the individual embossed foil webs in such a way that, due to the length differences of the various conveying routes the embossed foil webs arranged next to one another are offset in the conveying direction.
Preferably at least one embossing roller of the pair of embossing rollers has at least a first embossing pattern and a second embossing pattern.
A stack made of embossed foil webs for a vehicle heat shield according to the invention has neighbouring foil webs which have a different or parallel offset embossed pattern.
The stack preferably is such that the individual, embossed foil webs show deformations, in particular knobs, the said deformations having a draped or folded type structure.
Preferably the individually embossed foil webs have fissures.
The task set is solved by the invention with a process for the manufacture of a stack made of embossed foil webs. At least two unembossed foil webs are drawn from a feed device and are embossed between at least one pair of embossing rollers, and in particular are knobbed. The foil webs thus knobbed or embossed are then brought together in a stacking device into a stack. This stacking device also includes a cutting tool, in order to cut the foil webs which have been brought together into a desired length. According to the invention, a conveying device is provided between the pair of embossing rollers and the stacking device, with the aid of which the embossed foil webs are conveyed along various conveying routes. This conveying device is designed in such a way that at least two embossed foil webs arranged next to one another have to cover different routes before they are fed to the stacking device. Due to the differences in length of the various routes the embossed patterns on the various foil webs are offset to one another before the stacking device. In a preferred design form of the process as described in the invention, the foil webs are provided with different embossed patterns. Here individual knobs are embossed on the web which have a draped or folded structure. This draped or folded structure means that the individual knobs have a greater compression resistance and the whole foil web has higher bending strength. With this process it is also possible to create fissured foil webs, which are more acoustically effective than unfissured foil webs.
This process has the advantage that the webs made of flat or sheet material or foil webs which lie over one another can be embossed at the same time, preferably with a single pair of embossing rollers, which embosses all the webs lying over one another at the same time. A common structuring or embossing process of this nature, dispensing with a multiple number of pairs of embossing rollers, is correspondingly cost effective. In addition, an embossing pattern can very easily be changed by changing the pair of embossing rollers for a pair with a different embossing pattern. In particular, foil webs with a large number of different embossed patterns can be created very easily.
The process as defined in the invention allows foil webs which are lying on top of one another to be stacked with the embossed pattern offset or mismatched. In a further development of the process as described in the invention, the length of the individual routes taken by the foil webs in the area of the conveying device are set differently. In this way a different displacement of the embossed pattern can be achieved and the foil webs can be stacked in the desired manner.
The device described in the invention for creating a stack includes a feed device, a pair of embossing rollers, a conveying device and a stacking device. With this device, unembossed foil webs are fed to the pair of embossing rollers by the feed device. The foil webs thus supplied are embossed by the pair of embossing rollers in the desired way. According to the invention, the embossing rollers are structured in such a way that the foil webs are provided with a large number of knobs, so that these knobs have a draped or folded type structure. In a preferred further development of these embossing rollers, these are structured in such a way that the foil webs are provided with fissures when being embossed.
In a further design for this device, the first embossing roller has two different embossing patterns in the circumferential direction. The second embossing roller, which forms the pair of embossing rollers together with the first embossing roller, is designed to be opposed to the first embossing roller, so that the foil webs embossed in this way have alternately a first and then a second embossed pattern in the conveying direction.
In a preferred design the offset of the embossed pattern of the individually embossed foil webs is selected in such a way that two sheets arranged next to one another in the stack have a different embossed pattern, which means that the first embossed pattern of the one sheet comes to lie on the second embossed pattern of the other sheet.
With the device as defined in the invention, the embossing rollers are designed in such a way that through the embossing process in the flank area of the individual deformations, in particular knobs, the foil web obtains a draped or folded type structure. This draped or folded type structure in the individual knob flanks leads to a higher compression resistance for the individual knobs and the entire sheet material has greater bending strength. The reinforcement thus created also allows thinner foils to be used to achieve similar physical effectiveness, such as is achieved with known flat materials. Furthermore, the increased overall strength due to the draped or folded structure allows the manufacture of larger components without having to use an additional carrier or support metal sheet.
The stack as defined in the invention has a number of embossed sheets. These sheets are cut from the foil webs embossed and stacked in a mismatched fashion as described in the invention. An essential feature of this stack is that neighbouring foil webs have a different or offset embossed pattern. A further feature of the stack created according to the invention is that the embossed pattern has a large number of deformation with a draped or folded type structure. A preferred further design for this stack has fissured sheets.